Siemens SIMATIC RF600 System Manual page 60

RF600 system planning
4.3 Antenna configurations
EIRP
Directional antennas combine the radiation, and therefore have a higher power density in the
main beam direction compared to an isotropic radiator. To enable antennas of different
design or Directional characteristic to be compared with one another, the equivalent isotropic
radiated power (EIRP) has been introduced which represents the effective power which must
be applied to an isotropic radiator in order to deliver the same power density in the main
beam direction of the antenna.
"EIRP" is the product of the transmitted power P
EIRP = P
ERP
Also common is specification of the equivalent radiated power referred to the half-wave
dipole "ERP" (effective radiated power):
Logarithmic and standardized data
Approximate calculations are easier to carry out as additions than as products, therefore the
logarithms are taken for the above equations and the power data standardized to 1 mW and
specified in decibels (dBm or dBi).
Calculation of the radiated power with consideration of the cable loss a
If the transmitted power is not applied directly but via a cable with loss a
compensated such that the same radiated power is obtained.
If the loss is not appropriately compensated, the radiated power is too small.
58
* G
0 i
and the antenna gain G
0
k
System Manual, 05/2012, J31069-D0171-U001-A13-7618
:
i
, this loss should be
K
SIMATIC RF600